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I know that this is an older topic and that there was an answer given. But in my case that answer did NOT work.

I'm running indigo installed on Linux Mint 17.1 (based on Ubuntu 14.04 Trusty). I was having the same error as listed above and all the solutions I found didn't help. Until I did some digging.

I found that due to having more than one Python version installed the pip that was running by default was updating a different version of Python than ROS was using. So when I tried un-installing pyparsing and pydot and then installing newer versions there was no apparent change in behavior.

Trying to downgrade pyparsing gave an error and would not install the 1.5.7 version.

What I did find was that I had to explicitly run the version of pip from where the version of Python 2.7 being used by ROS was running on my system.

In my case this was sudo /usr/bin/pip install --upgrade pydot This caused pyparsing and pydot to be updated. Note that I got a message about not uninstalling pydot due to it being owned by OS, but this didn't impact the fix

Once the update completed rqt_graph is now working on my system.

You can do: which python To locate the directory where python is running from and double check where your pip is by doing: which pip

Both pip and python should be on the same path (e.g. /usr/bin in my case) but the default pip binary was being found at /usr/local/bin and not /usr/bin.

So I thought I would add this note for anyone who happens to be tearing their hair out with a similar issue.

Burt